Select the chart object by clicking on the caption. Then press <ctrl>-<shift> and hold. You will see a number of red boxes on the chart. Grab the one around the legend and move all the way to the top or bottom of the object. You should see the box change from vertical to horizontal (i.e. it will get much wider). When it does this, let go of the mouse.

I made whatever you suggested but here i am getting one more problem all charts are attaching i want gap between dimension names if i change in Bar settings under presentation tab then all bars are separating and giving confusion to users